The present invention pertains generally to plating apparatus and, in particular, to a novel plating rack with which a plurality of cylindrically shaped articles may be simultaneously plated.
In conventional plating practice, such as in chrome plating, etc., it is usually desired to obtain a substantially uniform thickness in the layer of plating deposited on the article or articles being plated. This is especially important where cylindrical piston rods having a circular cross section are to be plated, since variations in the thickness of the chrome plating layer can result in departure from a true circular shape. Where such piston rods are plated on a mass production basis, the techniques of the prior art leave much to be desired in attaining an accurate yet efficient process. Heretofore, groups of piston rods have been simultaneously plated in a plating bath with the aid of plating racks in which the articles are fixedly set. By way of example, these racks may include a contact beam, or contact bar, having a plurality of threaded holes at locations along the length of the rod into which threaded ends of the piston rods are threaded. The beam is usually oriented either horizontally or vertically on the rack with the piston rods being correspondingly oriented either vertically or horizontally. The rack is placed in the plating bath between a pair of anodes which are electrically coupled with the anode terminal of a source of plating current. The piston rods are electrically connected via the contact beam to the cathode terminal of the plating current source. Where the free ends of the piston rods are intended not to be plated, a protection screen is provided on the rack to screen these ends from the anodes. With this technique, the plating layer is of irregular thickness, typically oval. A further problem is that the number of piston rods which can be plated at one time is limited because each piston rod must face both anodes. In some racks, a row of piston rods is placed above another row of piston rods, and this has the disadvantage of exposing the piston rods in the upper row to gas generated by those in the lower row during plating which can adversely affect the plating of the articles in the upper row. Also, loading and unloading of the piston rods into and out of the rack is tedious. Although it is known in the art to rotatably support a single cylindrically shaped article in a plating tank during plating, as evidenced by U.S. Pat. No. 3,664,944, such a technique is hardly suitable for mass production plating of cyindrical articles.
Accordingly, the present invention is directed to a novel plating rack which enables a plurality of cylindrically shaped articles to be simultaneously plated with greater uniformity in the resulting plating thickness and with improved efficiency. Pursuant to principles of the present invention, the articles to be plated are rotatably supported in the rack for rotation about their longitudinal axes. With the rack immersed in a plating tank, the articles rotate in unison as plating current flows from each article to an anode which faces the rack. The features of the present invention include: improved facility in loading and unloading the rack; improved efficiency in supplying the plating current to the articles in the rack; and adaptability for articles of different lengths. These features are attained through novel plating rack structure including: novel gear and drive socket assemblies via which the articles are rotated and via which plating current is conducted to the articles; hingedly mounted protection sleeves for protecting the ends of the articles to prevent plating thereof; vertical adjusters at the sides of the rack for vertically adjusting upper and lower rack structure with respect to each other; an improved rack structure via which plating current is conducted from the cathode of the plating current supply to the articles mounted in the rack.